no you always use a dummy load then use the Lpad to drop the voltage by a known exact amount compatible to the sound card input I try for 1V p-p max under any condition ( lots of folks wreck sound cards ) assume any power source can come in contact with any of the test set up leads.
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Ok and just to be clear, you shoot for 1v out of the amp?
And did you see my post that the amp has adjustable gain? I know this isn't a volume attenuator, but I could still set the output to 1V given a set input level, no?
build a 6-10 dB attenuator as part of the 'Sound card protection scheme', run in loop back to zero the set up.
now you test for max power at some distortion, then use another (across the dummy load) attenuator to drop it back down to the amps input level.
always calculate your sound card in - output levels 1st before you test.
now you test for max power at some distortion, then use another (across the dummy load) attenuator to drop it back down to the amps input level.
always calculate your sound card in - output levels 1st before you test.
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calculator PI and T Pad Attenuator Calculator
Zo= input impedance of the sound cards 10-20K or just us an old 10K-25K pot with the wiper on the sound card dial it up to 10dB on the cal test. this will protect the sound card.
you can test this attenuator calc. thing in loop back without an amp so no worries
Lpad is simply 20LOG Rl/(Rl+Rs) when Rl = Rload Rs= Rseries > chose values 100-1000 times the dummy load ( so it doesn't affect the pad accuracy much ( remember loading of inputs outputs) like I said I just use the op-amps gain setting values for ease and convenience
Zo= input impedance of the sound cards 10-20K or just us an old 10K-25K pot with the wiper on the sound card dial it up to 10dB on the cal test. this will protect the sound card.
you can test this attenuator calc. thing in loop back without an amp so no worries
Lpad is simply 20LOG Rl/(Rl+Rs) when Rl = Rload Rs= Rseries > chose values 100-1000 times the dummy load ( so it doesn't affect the pad accuracy much ( remember loading of inputs outputs) like I said I just use the op-amps gain setting values for ease and convenience
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I decided to just measure the acoustic response of the woofer sealed near field since I was already setup to do it and I didn't have to figure anything out to make it work. I tried 1000uF and 2200uF. The extra extension is clearly visible; it's not a lot, around 10-15Hz lower, but that's fairly significant.
Unfortunately, I don't think those amps can put out anywhere near the rated output. They distort really easily past about half volume. And at half volume it's really very quiet still. I don't know if I may be clipping the input or what, I tried bringing the gain down and it helps, but of course it also makes it really quiet again.
My slightly modded lepai 2020A+ is miles better when I replace the little 18W chip amp with it. No distortion whatsoever. This is on the same 12v 2A power supply. I also have some 12v 5A supplies, but I can't seem to find them right now.
Any ideas as to why this should be happening? The data sheet for the tda2030 chip used in the 18w amp shows that it should produce 15w at 4ohms with .5% distortion on a 6v PS.
Unfortunately, I don't think those amps can put out anywhere near the rated output. They distort really easily past about half volume. And at half volume it's really very quiet still. I don't know if I may be clipping the input or what, I tried bringing the gain down and it helps, but of course it also makes it really quiet again.
My slightly modded lepai 2020A+ is miles better when I replace the little 18W chip amp with it. No distortion whatsoever. This is on the same 12v 2A power supply. I also have some 12v 5A supplies, but I can't seem to find them right now.
Any ideas as to why this should be happening? The data sheet for the tda2030 chip used in the 18w amp shows that it should produce 15w at 4ohms with .5% distortion on a 6v PS.
for increased volume use products designed for car audio, most use bridged tied loads BTL. bridging uses 2 amps per channel 180 degrees out, In theory giving twice the voltage into 4 ohms, so V squared/R gives 4 times the power. Class D squeezes even more by using saturating transistors instead of linear mode outputs. Also worth looking for high eff. speakers, a 3" driver can never compete with a 6 1/2 in.
there are even devices bumping Vcc higher, by using bootstrapped switching outputs.
also consider bigger batteries SLA don't droop as much as raw Li cells.
Li cells with boost DC-DC converter might be a consideration too, I haven't done that yet
there are even devices bumping Vcc higher, by using bootstrapped switching outputs.
also consider bigger batteries SLA don't droop as much as raw Li cells.
Li cells with boost DC-DC converter might be a consideration too, I haven't done that yet
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I knew the small driver was going to be a limiting factor as far as sensitivity, but i'm not talking about real room filling volume here just sufficiently loud without audible distortion. I'll take an spl measurement tomorrow to get a couple of figures.
Also, the drivers are set; I've already designed the enclosure and crossover and I'm very happy with the sound quality. Everything else is upgradable. Honestly, I expected to go through some trial and error with the electronics. I know what I'm doing with the speaker, but not so much everything else.
I can certainly look at other topology, but like I said I'm completely happy with the sound quality and volume I get with the 2020A T amp running one channel off a 12v 2A supply. The same supply that I get distortion at moderate volume with the other amp. I personally think the board or implementation is questionable. Or it simply requires a larger supply than they state. Based on the specs, I would think the two amps should be comparable as far as clean output.
The integrated Bt/amp module that's on the way (I think) uses a BTL. It uses the TDA7492P
I did get the other bluetooth module in today. It's a pretty nice piece and seems to work very well so unless the other one is as good I'd probably want to use this one and choose a different amp and battery.
HAHA! yes I know. That's why I said I think it either just doesn't have the chops or it's a bad implementation.
I've been looking around for something else anyways.
If I buy a stereo amp board, but only run one channel of it, is that safe for most chip amps?
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